This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A152772 #6 Apr 07 2024 09:10:05 %S A152772 1,0,1,1,3,3,5,6,7,9,9,13,11,15,15,19,15,24,17,27,23,27,21,39,25,33, %T A152772 31,41,27,51,29,48,39,45,39,67,35,51,47,69,39,75,41,69,63,63,45,97,51, %U A152772 78,63,83,51,99,63,99,71,81,57,135 %N A152772 a(n) = sigma(n) - 3*d(n) + 3. %t A152772 a[n_] := DivisorSigma[1, n] - 3 * DivisorSigma[0, n] + 3; Array[a, 100] (* _Amiram Eldar_, Apr 07 2024 *) %o A152772 (PARI) a(n) = sigma(n) - 3 * numdiv(n) + 3; \\ _Amiram Eldar_, Apr 07 2024 %Y A152772 Cf. A000005 (d), A000203 (sigma), A152770, A152771. %K A152772 easy,nonn %O A152772 1,5 %A A152772 _Omar E. Pol_, Dec 14 2008